Cancer treatment: Brachytherapy

Brachytherapy is a form of radiation therapy, by which a radioactive source is placed close to the tumor, either directly adjacent to it or inside the tumor itself. This procedure delivers a high dose of radiation to the target with only a minimal dose affecting the surrounding tissues.

Different modes of treatment

Brachytherapy uses sealed radioactive sources that are placed directly into tumors (interstitial) or in body cavities (intracavitary). One example is the implant of some 125Iodine inside the prostate gland, which deliver the required dose during the entire period they are active. More commonly, however, a radioactive source is inserted into the body and removed when the time calculated for the delivery of a specified radiation dose has elapsed. This time period needs to be determined by an oncologist.

Types of delivery

Treatment can be delivered according to the dose rate (dose given during a determined period of time) via:

Low dose rate (LDR) brachytherapy, which utilizes 137Caesium and Iridium sources, among others. In this technique, an ‘applicator’ is placed in the cavity or inside the tumor and the source is fed into the applicator, once the patient is in a shielded room. They remain in isolation until the source is removed (usually 12-24 hours). This process often requires hospital admission.

High dose rate (HDR) brachytherapy, which can be delivered with miniaturized sources of 60Cobalt or 192Iridium, which allows a dose rate greater than 12 Grays per hour, accounting for short times of treatment. For this reason, HDR can be administered as an outpatient treatment. Brachytherapy is a key component of radiation treatment for gynecological cancers. Other indications for brachytherapy include: prostate, breast, soft tissue sarcomas, some head and neck tumors, and skin cancers.